The previous threads about this error didn't help me out. The error message is misleading cause it's not about the video file specified in -f option, it's actually about Python not being able to invoke ffmpeg.
The solution that worked for me was this one: https://stackoverflow.com/a/64458721/494058
Open Anaconda Prompt, then run:
Once setup is complete, you should be able to run python ffmpeg-split.py -f GOPR7098.MP4 -s 180
Do you think it's worth adding this to README.md? Maybe a one-liner to verify whether ffmpeg is installed and accessible